I had a separate meter for my shop when I was in Iowa and it had a separate monthly bill. My tradeoff was the cost of copper for running a feed from the existing service vs. the extra monthly charges on the separate bill. I got double billed for all the extra charges: fees, regulation charges, etc., etc., etc. I was in a trailer park so I figured it was temporary and copper was at a high point at the time (post Katrina). So I just decided to pay the monthly charges. But if this is a permanent situation, you may want to sharpen your pencil before making the decision. You could easily be out many hundreds of dollars a year in future years.
In Florida I built an attached shop and the run was short to it so copper was cheap. I upgraded to 150 Amp service and added a sub panel in the shop. Worst cost was the copper from the pole. No problems with capacity ever.